Materials Supply Loss NHPP Activity 2D5

Research carried out 2011-2015 about the supply of traditional building materials, which are important to maintain the local distinctiveness and character of our built heritage. The work was part of the National Heritage Protection Plan.

Scope of the activity

Local distinctiveness is very often the result of the specific materials used in buildings and structures. If the sources of particular materials such as stone or thatch become unobtainable then that distinctiveness will erode and the character or significance of heritage assets and places will be diminished.

This Activity provided information on the sources of traditional materials, and support for practical techniques to maintain their supply. In the case of thatch, this included supporting studies into growing the raw plant materials for this type of roofing.

Projects in this activity

Strategic stone study

In historic buildings conservation work it is vital to obtain stone, which matches the original in its mineral composition, density and porosity. If not, new stone could hasten the decay of the original and is unlikely to weather in the same way, therefore looking very different.

To get a proper match, new replacement stone has to come either from the original quarry or at least from one in close proximity to the original supply. The rich diversity of England’s geology means that hundreds of different stone types have been used over the centuries for building purposes. However accurate information on the original quarries and the number and distribution of the buildings constructed from those stones is very scant.

The Strategic Stone Study aimed to address these problems by comprehensively mapping all the active, dormant and historic quarries within England, identifying the building stones they provided and matching them to buildings and structures. We worked with the British Geological Survey, local geologists and historic buildings experts from each county in England to identify the most important building stones used and representative buildings and the location of quarries.

Research into the supply of thatch

Concern over sufficient and suitable supply of thatching straw has been an issue for many years. The National Thatching Straw Growers Association is being funded to grow and monitor the performance of older 19th century varieties of wheat, which were known to have produced better thatch and be more resistant to bad weather.

The project consisted of two complementary and linked work packages. Firstly, growth trials of five wheat varieties are being carried out to monitor and evaluate the growing, husbandry and harvesting of the cereal crops, including the use of different fertilsers. This was followed by thatching small roof frames for long term annual monitoring of completed thatch with different types of thatching to assess the effect of treatment on longevity.

Artificial frosting of Collyweston slate

There are currently no reliable sources of good quality Collyweston slate. Nearly all the material used for repair and conservation is now reclaimed from other buildings, which is not sustainable in the long-term.

Furthermore the supply of materials is sporadic and the costs high. Artificial frosting, to prepare the stone slate for splitting and shaping, is essential to revive the dormant Collyweston stone slating industry. This allows reliable, year-round preparation of the lengths of stone known as 'logs' and therefore a higher volume of regular production: something that traditional outdoor frosting cannot provide.

Following research at Sheffield Hallam University to develop an artificial frosting process, large scale trials of Collyweston slate production using artificial frosting were carried out at Apethorpe Hall in Northamptonshire.

Collyweston roof

Expected protection results

Evidence to enable mineral planners to identify and investigate potential building stone sources to preserve and maintain local distinctiveness

Improved understanding of the issues surrounding the supply of thatch and the development of short-term and long-term response strategies